Lake Louise Winter Institute 20081 Outlook:  Introduction ...

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Lake Louise Winter Institute Rare B decays  LHCb Physics  CP violation in B system: using tree and penguins processes (NP)  Rare B decays: test FCNC (b  s) V. Gligorov  Rare B decays  FCNC has a pivotal roll: They are suppressed in SM, only realized via boxes or penguins NP can show up as the same level of SM Present results (i.e. b  sγ) strongly limit extensions of SM Indirect search of new particles: “visible” via loops  Experimental observables: ratios, asymmetries, branching ratios to leptons b  sγ Radiative decays: B  K*γ, Bs  Φγ Λ b  Λγ, Λ b  Λ * γ B  ρ 0 γ, B  ωγ b  sll : B  K*μμ, B +  K + μμ, B +  K + ee B q  ll Bs  μμ LFV B q  ll’ Bs  μe A CP (t) (Bs  Φ γ) A FB (B  K * μμ) β(Bs  μμ)

Transcript of Lake Louise Winter Institute 20081 Outlook:  Introduction ...

Lake Louise Winter Institute Outlook: Introduction LHCb performance Radiative decays: CP violation Bs Backward-forward Asymmetry B K * Branching ratio of very rare Bs Conclusions Prospects for rare B decays in LHCb Jose A. Hernando (CERN, on leave Universidade de Santiago de Compostela, Spain) [On behalf of the LHCb collaboration] Lake Louise Winter Institute LHCb experiment and conditions Luminosity range cm -2 s -1 Nominal integrated luminosity 2 fb -1 / year (10 7 s) bb produced/year B, Bs, B + But large backgrounds and small BR 0(10 -6 )of relevant decays 10 MHz visible interaction (1% bb) Total10 fb -1 P. Vazquez Lake Louise Winter Institute Rare B decays LHCb Physics CP violation in B system: using tree and penguins processes (NP) Rare B decays: test FCNC (b s) V. Gligorov Rare B decays FCNC has a pivotal roll: They are suppressed in SM, only realized via boxes or penguins NP can show up as the same level of SM Present results (i.e. b s) strongly limit extensions of SM Indirect search of new particles: visible via loops Experimental observables: ratios, asymmetries, branching ratios to leptons b s Radiative decays: B K*, Bs b , b * B 0 , B b sll : B K*, B + K + , B + K + ee B q ll Bs LFV B q ll Bs e A CP (t) (Bs ) A FB (B K * ) (Bs ) Lake Louise Winter Institute Bs Motivation: Inclusive BR in agreement with SM LHCb can perform exclusive measurements And test the polarization In SM is b s is predominantly (at 0(m s /m b ) left handed CP violation in the mixing and decay depends on the polarization Measured in B K*(K s 0 ) A CP at Belle[3], BaBar (S K* = 0.310.05) [4] LHCb can measure time-dependent CP asymmetry of Bs [1]NNLO [2]HFAG [1] hep-ph/ [2] arXiv/ hep/ex [3] hep-ph/ , Phys.Rev D72, [4] arXiv/ hep/exp [5] hep-ph/ [ 5] SM: C~0, S~-0.10.1%, A ~ sin2 fraction of wrong polarization A CP (t) (Bs ) Lake Louise Winter Institute A CP (t) for B s Full detector simulation main background bb (37 M) Selection Et() > 2.8 GeV, Yields (2 fb -1 ): Total efficiency ~ 0.3% Background bb inclusive: B/S ~ 90 CL Issues: Acceptance function a(t) (t) as function of topology MC stats: 37 M bb events 2 fb -1 (A )0.20 (S,C) fb -1 B K* 72 k Bs 11 k Lake Louise Winter Institute A FB (B K * ) Motivation: BR in agreement with SM (B K*) But NP can show us in angular distributions A FB asymmetry vs m 2 Decay described with 3 angles ( l,, K* ) A FB of in l vs m 2 SM zero point well predicted: SM: [1] GeV 2 BaBar and Belle [2] Measurements [1] hep-ph/ [2] hep-ph/ A FB M 2 (GeV 2 ) BELLE 06 m 2 [GeV 2 ] A FB (m 2 ) theory illustration Lake Louise Winter Institute A FB (B K * ) Yields Efficiency ~ 1% Background B/S 90% CL bb: b ,b bb: b ,c (c ) Issues Acceptance function a( l,m 2 , ) Sensitivity 0.07 fb -1 competitive with BaBar & Belle An example 0.5fb -1 experiment An example 0.1fb -1 experiment M 2 (GeV 2 ) A FB 2 fb -1 B K* 7.3 k 0.5 fb -1 2 fb fb -1 (s0)0.8 GeV GeV GeV 2 Lake Louise Winter Institute (Bs ) Motivation Bs very rare Helicity suppress (m /m B ) 2 SM well predicted SM: (Bs ) = (3.550.33) x Very sensitive to (pseudo) scalar operators MSSM ~ tan 6 /M 4 A MSSM (NUHM) fit favor large tan ~ 30 g-2 results (deviate from SM 3.4 ) Current limits [2] CDF BR < % 2fb -1 [3] D0 BR < % CL [1] arXiv: v1 [hep-ph] [2] arXiv: v1 [hep-ex] [3] arXiv: v1 [hep-ex] [1] Lake Louise Winter Institute (Bs ) Small signal and large background, but Efficient trigger: ~1.5 kHz inclusive . Di- Mass resolution: ~20 MeV Vertexing: GL: Combine geometrical variables Background: Main background (b ,b , b , b c ) B hh, small compared with b ,b Bc + J/ dominant of exclusive, but still small Analysis: Divide (GL, Mass) space in N bins Expected events/bin for signal, signal+bkg Yield : Total efficiency ~10% (all GL values) S ~30 events, Bkg ~ 2fb -1 (GL>0.5) Control channels: Signal description: B hh ~200 2fb -1 background (from sidebands) Normalization: B + J/ K + 2 2fb -1 Red: signal Blue: bb inc. Black: b b Green: Bc+ J/ GL (geometry) Mass (MeV) Bs Bs KK arbitrary units Lake Louise Winter Institute x10 -8 (~0.05 fb -1 ) 5x10 -9 (~ 0.4 fb -1 ) Integrated luminosity (fb 1 ) BR (x10 9 ) Uncertainty in background prediction Expected final CDF+D0 limit SM prediction 90% CL imit on BR (only bkg is observed) [1] arXiv: v1 SM agreement 2 fb 1 3 evidence 6 fb 1 5 observation Exclusion: 0.1 fb 1 BR < fb 1 < SM (Bs ) [1] Lake Louise Winter Institute Conclusions LHCb finishing installation, getting ready for 1 st collisions Rare B decays in LHCb will constrain extensions of SM or find NP Already with first year data 0.1, 0.5 fb -1 Bs excluded at SM value with 0.5 fb -1 A FB (B K*) (s 0 ) ~0.8 GeV 0.5 fb -1 And above 2 fb-1 Bs evidence if SM 2 fb -1, observation 6 fb -1 B K * (s 0 ) ~0.5 (0.3) GeV 2 (10) fb -1 other observables: A (2) T, F L Bs A CP asymmetry >2 fb -1 Lake Louise Winter Institute Particle ID -K separation: Kaon ID ~ 88% Pion mis-ID ~ 3% ID B q hh (~0.5%) 2 (mu-ID eff 95%) LHCb expected performance Mass resolution Vertexing (Mass) Bs ~20 MeV B K* ~14 MeV Bs ~90 MeV (proper time) Bs ~ fs Trigger: L0 2 HLT B signature : large Pt and displaced tracks HLT: ~ 1.5 kHz + di- inclusive sample efficiency (L0xHLT) Bs ~90 % B K* ~70 % B ~40 % P. Vazquez Lake Louise Winter Institute A (2) T,F T (B K*) Other observables [1] in B K* Expresed in terms of transversity amplitudes Fit individual angular distributions ( l,, K* ) vs m 2 2 fb -1 Asymmetry A T (2) Longitudinal polarization F L SM NLO MSSM tan =5 2 fb 1 10 fb 1 A T (2) 0.42 0.16 FLFL A FB Sensitivity with [1] hep-ph/ An example 2 fb -1 experiment